Abstract

The objective of this thesis was to investigate the synthesis of well defined star polymers utilisingcontrolled radical polymerisation techniques for potential use as viscosity modifiers in Engine oils.Recent developments in the characterisation of star polymers using multi-detector GPC wasinvestigated by first synthesising a series of star polymers using a core-first technique and ATRP.Core-first initiators were used to initiate the polymerisation of PMMA star polymers which werethen analysed using multi-detector GPC. Using Zimm and Stockmayer theory the functionality, f,(number of arms) of the resultant star polymer was estimated over the MWD of the polymer usingGPC with in-line viscometry. A variation in functionality with molecular weight was seen, whichdisagrees with the limited other literature in the field.The GPC technique was then used to determine the functionality of star polymers synthesised usingRAFT polymerisation and an arm-first technique to yield star PMMA with a high Mw and PDI. Varyingthe divinyl species and the ratio of [crosslinker] to [macroRAFT agent] was seen to control thefunctionality and molecular weight of the star formed. Varying the amount of monomer present atthe point of crosslinking was seen to have little contribution to the star polymer formed when theratio of [MMA] to [macroRAFT agent] was under 10.Switching RAFT agents from 2-cyanoprop-2yl dithiobenzoate (CPDB) to an oil solubletrithiocarbonate, for the RAFT polymerisation of long chain alkyl methacrylate gave hybridpolymerisation kinetics. Through a monomer feed system, controlling the ratio of [monomer] to[RAFT agent] throughout the reaction, polymers of narrow PDI were synthesised and subsequentlycrosslinked to form oil soluble star polymers.Applying the techniques used for the synthesis of core-crosslinked star polymers using RAFTchemistry to different area of polymer chemistry, glycopolymers; a series of linear mannose andgalactose bearing glycopolymers have been synthesised. Trimethylsilyl propargyl methacrylate (TMSPgMA) has been polymerised to varying DP, between 20 and 200, using CPDB as the RAFTagent. Subsequent deprotection of the propargyl groups has yielded a series of alkyne bearing linearpolymers. Using a CuAAC reaction to "click" mannose and galactose azide to the polymer scaffoldsyielded well defined sugar bearing polymers. A P(TMSPgMA) macroRAFT agent was crosslinked usingdifferent crosslinkers to giving a high molecular weight, alkyne bearing, star polymer.